This invention relates generally to dishwashers of the household undercounter type, and more particularly to the supporting structure for a sliding rack of the upper rack type mounted on the side wall of the dishwasher tub.
The typical dishwasher of this type has a downwardly opening hinged door which pivots through 90 degrees to a horizontal position. The dishes and other items being washed are carried on two wire racks specially configured to hold the items, with pans and large plates usually on the bottom or lower rack and glasses, cups and similar pieces usually placed on an upper rack. The lower rack is usually provided with wheels which roll along rails or ledges formed on the tub walls in alignment with the inner surface of the door in the open position. This allows the lower rack to be rolled on the wheels out onto the inner face of the open door for easy loading and unloading.
The upper rack presents more of a mounting problem because it must be mounted on the side walls of the tub. Since the upper rack is close to the top of the tub, it must be movable almost all of the way out of the tub for loading and unloading, and this requires that the rack be movably supported on an intermediate channel or rail, which in turn is movably supported on the tub wall. A well-known arrangement for supporting the upper rack is the use of a generally C-shaped channel or rail having the open side facing the interior of the tub. The channel is positioned and journaled for horizontal movement by at least two pairs of vertically spaced support rollers on the side wall of the tub near the front and middle portions of the tub. The rollers are grooved to receive the rounded upper and lower edges of the channel to allow it to slide freely in a horizontal direction parallel to the tub wall, but restrain the channel against any vertical movement or any transverse movement away from the tub wall. The upper rack has on each side at least two projecting rollers which fit within the channel with a minimum vertical clearance to positively position the rack with respect to the channel, yet allow the rack to slide freely along the channel. Thus, the upper rack can roll along the channel as the channel rolls along the supporting rollers on the tub so that the rack can slide far enough with the channel to move completely out of the tub, with the channel moving about half of the total movement of the rack.
While the foregoing arrangement has been widely used, it has been recognized that one of the problems has been the provision of a stop at each end of the channel to prevent the rollers on the rack from escaping from the channel. Since the channel is generally formed with open ends from relatively thin sheet metal such as a stainless steel, it is recognized that it is necessary to place a stop member at each end of the channel to retain the rack rollers and prevent the channel from moving out of the support rollers. To allow the upper rack to be easily removable for cleaning or repair, the stop member should be easily removable as well as easily replaceable without the use of any special tools, while being of sufficiently low cost of manufacture.
Another function of the stop member is to provide a resilient bumper for the rack rollers when they reach the end of the channel so that they do not make a noisy impact with the stop member or produce a sharp impact which might cause fragile items on the rack to be broken.
One arrangement which has been used is a stop member or bumper formed of a relatively soft rubber which fits within the channel and is held in place by an elongated pin extending vertically through the top and bottom walls of the channel and through the body of the bumper, as shown in U.S. Pat. No. 4,097,098. This arrangement is relatively expensive and requires the use of two pieces, with the risk that the pin can be easily lost by the user during removal and replacement of the bumper during ordinary use. Other arrangements include the use of relatively complex snap-in plastic pieces such as those shown in U.S. Pat. Nos. 3,982,802 and 4,437,715. However, these arrangements require careful manipulation during removal and replacement and are subject to possible over-stressing and breakage, resulting in failure of the part.